


Repentance and Sin

by Darling in Devildom (kylobenrensolo)



Series: Rise and Fall (ON HOLD) [3]
Category: Shall We Date?: Obey Me!
Genre: Biting, Biting with blood, Blood, Blood Kiss, Blood and Injury, Body Horror, Body Modification, Bones Breaking, Breast Play, Burning flesh, Consensual Sex, Cunnilingus, Demon Blood, Demon Sex, Demon cock, Descriptions of Pain, Dom/sub, F/M, Female POV, Jealous sex, Multiple Orgasms, Orgasm Control, PWP, Painful Sex, Penis In Vagina Sex, Rough Sex, Smut, Tail Sex, aggressive domination, bdsm sex, could be seen as self injury, demon transformation, female!MC, oh boy where do i start with these, you are turning into a demon and its really graphic
Language: English
Status: Completed
Published: 2020-08-21
Updated: 2020-08-21
Packaged: 2021-03-06 17:41:22
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 3,622
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26032837
Author URL: https://archiveofourown.org/users/kylobenrensolo/pseuds/Darling%20in%20Devildom
Summary: “A toast? To forever?”“Forever.”You made your choice and now, not even time can save you from the consequences. Your weak, pliable form is stripped away from you, but what is to come when you are left with nothing but familiar, overwhelming sin coursing through your veins. Are you truly stronger? Is love more powerful than the new force rising?
Relationships: Asmodeus & Main Character (Shall We Date?: Obey Me!), Asmodeus (Shall We Date?: Obey Me!) & Reader, Barbatos (Shall We Date?: Obey Me!) & Reader, Beelzebub & Main Character (Shall We Date?: Obey Me!), Beelzebub (Shall We Date?: Obey Me!) & Reader, Belphegor & Main Character (Shall We Date?: Obey Me!), Belphegor (Shall We Date?: Obey Me!) & Reader, Diavolo (Shall We Date?: Obey Me!) & Reader, Leviathan & Main Character (Shall We Date?: Obey Me!), Leviathan (Shall We Date?: Obey Me!) & Reader, Lucifer & Main Character (Shall We Date?: Obey Me!), Lucifer (Shall We Date?: Obey Me!) & Reader, Main Character & Mammon (Shall We Date?: Obey Me!), Main Character & Satan (Shall We Date?: Obey Me!), Main Character/Mammon (Shall We Date?: Obey Me!), Mammon (Shall We Date?: Obey Me!) & Reader, Mammon (Shall We Date?: Obey Me!)/Reader, Satan (Shall We Date?: Obey Me!) & Reader, Simeon (Shall We Date?: Obey Me!) & Reader
Series: Rise and Fall (ON HOLD) [3]
Series URL: https://archiveofourown.org/series/1876309
Comments: 12
Kudos: 98





	Repentance and Sin

**Author's Note:**

> Hi everyone! Welcome back!
> 
> "Repentance and Sin" is part of my Obey Me! series, "Rise and Fall", so if you haven't checked out the first two parts yet, please do before reading this!
> 
> Boy, this one is a doozy. 
> 
> Please, before proceeding, read over the tags if you haven't already. This fic is a PWP (Porn with Plot) with many descriptions of pain, body modification, and demon sex. 
> 
> BUT! Have no fear! If you are enjoying this story and this type of fic isn't for you, you DO NOT need to read it to continue the story from here. All you need to do is read the prelude and the epilogue and I will be summarizing any important details from the main story in the endnotes. The dashed lines will signify the end of the prelude and the beginning of the epilogue. 
> 
> And with that, please enjoy.

“So, what is it exactly?” You stood before the Demon Lord, studying the vial in your hands. You held it up to the light; it seemed to glitter like diamonds, while also having a velvety quality to it. 

“I do believe Lucifer is rubbing off on you, dear human.” He chuckled. “He was rather inquisitive of the potions origin and make as well.”

“That’s what it is then? A potion?” 

Diavolo let out another deep laugh and walked around his desk to meet you on the other side. He placed his large, heavy hands on your shoulders and gave them a gentle rub.

“You may be the only human to ever be offered everything they desire and still find a way to question it.” 

“Please don’t think I’m not grateful, Lord Diavolo. I am. A _ton_. I’m just nervous.” 

Barbatos entered the room, placing a serving tray of tea and biscuits on Diavolo’s desk for both of you to share. He moved to the side of the room, out of the way, but standing to attention in case his master required anything else. 

“Completely understandable, my young friend. I won’t lie and tell you won’t be painful, but once it takes its course, you should begin to possess the healing qualities of a demon and the rest of your transition should run smoothly. Does this put your mind to ease?” 

Diavolo’s eyes flicked over to catch his servant’s before coming to meet yours once more.

“Yes. Thank you.”

\----------------------------------------------------------------------------------------------------------------------------

At first, it made you want to scream. You could only imagine it was what battery acid would taste like. You held the first few drops you could manage in your mouth, forcing your body to hold it against your resisting tongue. You could have sworn it was burning holes through it. Perhaps it was. 

Your arm shook in fear instinctively, knowing it would be the one to seal your fate and force the liquid further down your throat. He was immediately by your side, gripping you. He looked like he was going to force you to stop, unable to handle the muffled screams of pain you made around the rim of the glass, but he seemed unsure what would happen if you stopped now and didn’t consume it all. With the only strength you had left, you threw the glass back and attempted to widen your throat as much as you could, hoping to let no further hit the inside of your mouth. 

The feeling of what could only be described as broken glass hitting every inch of your throat down into your stomach had you on the ground in seconds. Luckily, Mammon was there to make sure you didn’t hurt yourself further as your back pressed against the floor. Your ears were ringing and you had no idea where your yells stopped and Mammon’s started. He called out for anyone who could hear but was met with no response. 

Your body seized in his arms, every muscle contracting and warping like it was preparing for something new. Your throat clenched, letting out a sharp gasp before you were lifted. 

Your eyes snapped open, the pain suddenly missing from your body. But you were no longer in the usual comfort of Mammon’s room, in your lover’s arms. His back was to you, but you knew who it was already, his smaller companion by his side. He let out a sudden pained gasp, kneeling and grasping his chest. He whispered something you couldn’t quite make out before whipping around, dark locks swaying with his movements. Your eyes almost caught before you fell. 

It was the world’s deadliest roller coaster of drops. The flesh of your back burned and singed as the three realms were a blur in your peripherals. Then, you landed. 

You expected to crash through Mammon’s floor to somewhere even deeper in Hell, but as your soul rejoined its shell, something brought you swiftly to your feet. It wasn’t until you heard a stumble to the floor in front of you that you opened your tightly sealed eyes. Mammon, now in his demon form, sat on the ground a few feet away, hands next to him like he had crawled back in fear, donning a bright red, blotchy, tear-stained face. His screams in terror over your mangled body were now replaced with a fearful gaze to something just behind you. Then, you felt it.

You felt it like every nerve in your body was on fire and magnified times a thousand. The soft, comforting brush of feathers. 

Your brain was daring you to look over your shoulder, but you were unsure if you could even manage it. Like they could read your thoughts, they brought themselves forward so you could look without moving at all. As you took in the sight of your new organs, there was only one word that came to your mind. Well, name. 

**  
Lucifer.**

  
Your wings were magnificent and almost an exact replica of his. Except you only had one set and there were a few gray feathers mixed in with the midnight black. 

Upon their sight, you had almost forgotten about the terrified, shaking demon before you. Your wings had been reliable enough so far, so you decided to try and take a step towards him. Then, it hit you. 

It was like the reality of the situation finally struck, even though it felt more like twenty buses. Your chest tight, legs giving out, bringing you to your knees. Nearly every bone in your body had broken. Not only from the transformation but from Mammon’s attempt to resuscitate you in the few moments you had been, in all senses of the word, dead. 

Snapping out his trance, his hands were on your waist, stabilizing you. Another howling scream released from your lungs as you placed your hands on Mammon’s shoulders. He hissed as he felt them crack and fuse before being replaced with sharp claws piercing his back. He could feel the blood running down the vastness of his skin, but did his best to maintain his tight hold on you, never letting go. 

More bones were quick to fuse and take shape to your new form, forcing your face down at the freezing tile between your and Mammon’s bodies, screams bouncing off it. As the discs of your spine melded with your wings, your head snapped up, eyes finally meeting Mammon’s. His mouth fell open in shock. You couldn’t see it yet, but your eyes shined a deep, daunting purple. 

**  
Beelzebub.**

**Belphegor.**

  
A complete set of three once more. The only thing your body could do was let out small exhausted whimpers as it set and prepared for the next inhumane change. 

“Mam-mon.” It was raspy and weak, but it fell from your lips like a plea. “Help… me. Make… it stop.”

He let out his own whine and whimper like he could feel every horrible thing your body was experiencing. Your pleas for help from him reminding him so much of your early days together. He placed a kiss to your forehead and you could feel the wet warmth of his frightened tears. Suddenly, there was fire, but it wasn’t on your skin. 

It flowed through your chest, stomach (which, through all the pain, felt like it was going to implode with hunger) and shot all the way down. Coming from a place you were unaware you now had, an animalistic growl flowed through your lips before you connected them with his. The fire of your connected lips almost completely subsided the pain coursing through your body, so when he attempted to back away from you, you bit down on his lip. Hard. He flashed you a bewildered look at your sudden aggression. 

“Please, Mammon.” You choked out. “Please… please… it helps the pain. Please help me.” 

You cried out the last words, but Mammon didn’t let it last long. His lips were quickly back on yours with such force you could feel them bruising. You dragged your hands forward to the front of his chest. His hands pulled carefully at what was left of the torn shreds of your dress. But as you ran your hands over his toned pecs, claws leaving deep scratches in their path, he ripped the front open, breasts spilling out. 

He was quick to move one of his hands from your side to cup one of tits, kneading it harshly. A guttural moan fell out of your mouth, giving Mammon the chance to force his tongue inside. His greed reared its ugly head, never allowing your tongue to explore the inside of his mouth, determined to drink the taste of you. 

While your new submission to lust had substantially subsided the pain, you couldn’t ignore it when it moved to the top of your head. When he felt you whine against his mouth and reach one of your hands up, he pulled back momentarily. 

The disconnect brought back every sensation of pain and only increased your hunger. Your hunger for him. Regardless, you brought your other hand up to the top of your skull as well where you felt two large bumps under your skin threatening to burst through. 

Unable to control your newly acquired strength, your claws reattached to Mammon’s skin, deep enough to raise him to his feet and push him back against the wall. Your wings were quick to lift you and help you meet him once again. The pain in his raw skin spurred him on further, causing the newly formed erection in his pants to grow even harder and ache deeper for you. 

He placed his arm against your chest, switching places with you and forcing you against the wall instead. He made quick work of attaching his lips to your neck, letting them trail down your chest. As he went to examine his work, he found not only bright red welts but black diamond markings seared into your skin. 

**  
Leviathan.**

  
He growled at his brother’s mark against his human’s flesh and was quick to find one of your nipples in his mouth, determined to leave his own mark. 

“Mammon… fuck!” 

His name resembling a mantra on the tip of your tongue. You sounded so delicious calling out for more, he decided to reward you with a leg between your thighs and a hand gripping your hair. You graciously accepted the knee now grinding up against your cunt, but it wasn’t hair that Mammon grabbed on to. He glanced up from his relentless nipping and sucking on your nipple to see his hand wrapped around a smaller, twisted black horn. 

**  
Asmodeus.  
  
**

He curiously dragged a thumb against the smooth surface, eliciting a moan from you that caused your arch your back against the wall further. His knee kept you standing but forced you to grind even  
harder against it.

“FUCK! MAMMON!” 

You swayed your hips against his leg, wondering if he could feel you practically dripping through your panties and on to his pant leg. 

“PLEASE. PLEASE FUCK ME MAMMON.” 

You snapped at him like a feral animal, fighting back against his hand on your stomach, attempting to claw his remaining layer of clothes off his body. 

Even when he reprimanded your actions by biting down on your nipple, it only caused it to harden more in his mouth. Your pride did not take well to his domination over you and your rabid brain did the only thing it could think of in the moment. You pulled him up to meet your face, causing him to detach from your nipple, and sunk your teeth into his neck. 

Before tonight, Mammon always loved having you suck and bite on his neck, even though it didn’t do too much damage thanks to his thick demon skin. But now, the metallic taste of his blood filled your mouth. 

He grunted and hissed, but allowed his head to fall back, gifting you more access to his skin. You released the bit of flesh between your teeth and began to pierce whatever random bits that you could find. 

You could feel his rock solid erection twitch against your thigh at your assault on his neck. You went to reach down to palm his large, begging cock through his pants, but his whimpering moans suggested there was no need. You twitched at an unfamiliar sensation filling your body, Mammon’s hand guiding your newly released black, velvet tail to stroke the outline of his cock. 

**  
Satan.**

  
The stimulation of having your appendage brush strokes against him expertly and your mouth work tirelessly by his jaw was too much. If he didn’t stop you now, he’d surely cum. 

Growing tired not being inside you, he placed both his hands at your shoulders and shoved you back from him hard enough to form a crack in the wall. 

Before he could attempt to make sure you were okay, he was caught off guard in the best way possible by the sight before him. Your violet eyes were blown wide with lust, sweat dripping down your horns, marks glowing bright, wings and tail swaying seductively, and, in your mouth, a set of beautifully sharpened fangs, dripping with his blood. 

**  
Mammon.**

  
Your transformation was complete, each pact, each brother efficiently having made their mark on your new demon form. 

You were beautiful. You were _his_. It was time to show you. 

He made quick work to kneel before you, almost as if to pledge his loyalty to you. He used his own sharpened teeth to grab at and rip the remains of your dress and panties swiftly from your body. He pressed needy kisses against the now exposed skin of your stomach and thighs, just barely missing where your body begged for him the most. 

“Mine… mine… mine…” he growled between each kiss. 

If you thought Mammon was possessive of you as a human, it was nothing compared to how he felt about the gorgeous demoness currently captive to his touch. 

When he finally placed a wet kiss to the mound of your pussy, your hands shot to his horns, gripping them tightly. He wrapped his arms around your legs and placed his hands to the underside of your thighs, lifting them to rest on his shoulders. When he felt you were secure in his hold, he let his burning desire take control. 

He scraped his fangs down your mound, letting his hot breath fall out of his mouth, hitting your pussy deliciously. You squirmed, attempting to find any contact between his lips and your awaiting cunt. His bottom lip grazed your clit and you swore you could release right there and then. But you didn’t. That is until he swiftly wrapped his lips around the nub and harshly sucked. You were quick to let out a screaming release, forcing Mammon to move from your clit and focus on your now drenched folds, not wanting to miss any drop from you. His expert tongue pressed hard against your opening as you threw your head back. 

He snaked an arm around your back before suddenly rising to his feet. He placed firm hands on your ass, helping your thighs release from his shoulders and slide down to wrap around his sides instead, your opening almost aligned with his still clothed cock. Using his free hand, he was quick to slide his pants down enough to release his member from its confines. 

He pumped it in his hand once before slapping it against your stomach, the tip red and angry with a small amount of precum smeared on the tip. Showing it off for you. Demon cock was no joke and Mammon was no exception. Every time you fucked, there was always a small worry in the back of your mind if you’d be able to take it while he focused on not breaking your fragile human body. Now, nothing was holding either of you back. 

His lips crashed against yours once more, able to taste his blood on your tongue and you, the remains of your first release. He teased your folds with the head of his cock, occasionally slapping it against your clit. But your whines to be filled were only met with his signature shit-eating grin against your open mouth. 

What seemed like endless taunting forced you to take matters into your own hands. You lightly bit down on his tongue causing him to, in surprise, release his cock from his hand long enough for you to grab it and plunge it into your waiting heat. 

His tongue snapped back into his mouth as he bit back a grotesquely sensual moan on his lip. He gave you no time to adjust, needing to feel you clench around his cock probably just as bad as you needed to do it at this point. 

Usually, he’d make the moment last. He’d make sure he felt and remembered every inch of your walls. But this… was relentless. His hips snapped against yours with a record-breaking pace. Usually, it was Mammon being chased, but right now, Mammon was doing the chasing. He was chasing his own release and he wouldn’t stop until he filled you to the brim and felt you cum all over his cock. 

His groans all ended with muffled cries, especially when you started fucking yourself on his cock to meet him. He pressed your back to the wall, gaining more leverage and a better angle to hit the spot in you he was always so excellent at finding. You screamed each time the curve of his cock pressed against the spongy flesh, wings shaking along with the relentless pounding to your core. The heat was building up again after your previous orgasm causing your walls to flutter around Mammon’s cock causing him to twitch inside you. 

His new erratic thrusts and needy cries told you he was close so you reached out to the arm that wasn’t supporting you and guided his hand to your clit. He snickered at your plea for more contact, pressing the pad of his thumb to your tight bundle of nerves before making quick swipes against it in time with his pumps. Your pussy clenched so tight around him, it almost made it hard for him to continue his strokes. Your jaw went slack in ecstasy, but Mammon was quick to grab it and bring your attention to his face, slowing his pace and stopping the motions on your clit. 

“You fucking look at me when you cum. I want to hear you scream my name or I’ll stop. I swear to Diavolo. Nod if you understand.”

You weakly nodded in his grasp before he kissed you gently. Taken by aback at his sudden soft gesture, you were nowhere near prepared for when his cock resumed his pace and his thumb began toying with your clit again. You tried to instinctively throw your head back, but his grip on your jaw became tighter, keeping your eyes on his. He fully drew his cock out and roughly thrust back in, finding your spot once more. Your pussy gripped his dick for dear life and he finally heard the words he wanted nothing more than to hear for the past week.

“FUCK! MAMMON! I’M YOURS, MAMMON. ALL FUCKING YOURS. FUCK I’M CUMMING.” 

You attempted to let your eyes roll back, but he shook your head, forcing you to refocus. The devilish glint in his eyes was enough to do it. You shook and screamed out his name continuously, cumming hard on his monstrous demon cock. Your wings wrapped around the two of you, even reaching behind him to stroke against his leathery, bat-like ones. The combined juices dripping down his cock and gliding over his balls was enough to force him to his imminent orgasm. 

“DEVILS. FUCK, MC.” 

He cried, giving one more hard pump into your already highly overstimulated pussy before cumming deep inside you. You could feel its warmth fill and soothe your aching insides and slip down your thighs. He rested his face against your bare chest, deep harsh breaths escaping from him as he felt his cock slip from your pussy and go limp between his legs. 

After a moment, he placed both hands next to the base of your wings, bringing your chest to his. You felt your eyelids begin to droop as your own heavy breaths hit his chest. The heaviness on your back and head seemed to disappear inside of you as you shifted back to your familiar human form. He carried your limp, exhausted body to his bed, laying you down in the center gently against the silk sheets. 

He went to slip in next to you but stopped in his tracks. Similar to the beginning of your transformation, Mammon felt a horrid pain stretch through his entire being. He stumbled forward, gripping the covers next to you, confusion and fear covering his face once again. 

That’s when you heard the screams. 

\----------------------------------------------------------------------------------------------------------------------------

Lucifer knuckles clenched against the back of the wooden chair, turning a sickly pale color. The sound of splinters breaking off and hitting the cool tile below filled the room. He let out a loud, animalistic snarl, wings unfurling from his back, shaking and attempting to wrap around and protect his form. 

A large hand was placed on his shoulder, squeezing and holding him in place to keep him from falling to his knees. Lucifer went to pull away, but another surge of pain ripped through his body, causing his back to arch inhumanely and head to face the ceiling of the palace. Another guttural, low cry came from his lips. Diavolo observed his state, a blank unreadable look on his face. Then, Lucifer could have sworn, a grin.

“It’s happening.”

**Author's Note:**

> As promised, here's a short description of all the important takes from this chapter.  
> MC takes the "potion" and begins her demon transformation. The transformation kills her and she is momentarily taken to the Celestial Realm where she sees Simeon and Luke, who seem to be able to sense what is happening, before falling back to Devildom. In her demon form, she gains one demon likeness from each of the brothers and is influenced by each of their sins. Giving in to these sins are the only thing that is able to soothe her pain. As things calm down with Mammon, he starts to feel a familiar pain to her transformation, and screams are heard throughout the House of Lamentation. 
> 
> I have to quickly thank each and everyone one of you who has read this series. As of yesterday, the series has hit over 1,000 reads and I could not be more overjoyed. As always, the vision board for the fic will be on my twitter @devildomdarling !  
> Also if you came here from Tiktok, welcome! If you haven't seen the tiktok about my series, I mentioned that I was laid off from my dream job the day after I posted Mortality and Eternity. In the endnotes of that part, I said that writing this fic became my therapy and now, it is more so than ever. So thank you, thank you, thank you for continuing to read.
> 
> Installment 4, Succumbence and Vice, is coming soon!  
> Things aren't always as they seem.


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